Packet analysis apparatus and method thereof

ABSTRACT

A method executed by a packet analysis apparatus for analyzing packets including voice packets and non-voice packets includes: capturing packets in a specific session; storing the captured packets in a storage; screening the stored packets to count up a receipt count of voice packets; determining whether packet loss has occurred in the specific session; and determining whether loss packets are voice packets in accordance with received packets adjacent to the loss packets to count up a loss count of voice packets when the packet loss has occurred.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2009-145938, filed on Jun. 19,2009, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a packet analysistechnique.

BACKGROUND

With the developments in information communication technologies,bi-directional communication via packet communication networks has beenin widespread use. In particular, Internet protocol (IP) telephones thatfacilitate voice communication via an IP network (e.g., the Internet)have been in widespread use. Such IP telephones employ a voice overInternet protocol (VoIP) in which packetized voice data is transmittedand received via a packet communication network. Accordingly, it isimportant for service providers that provide an IP telephone service tomonitor and manage the quality of voice of an IP telephone.

In order to measure the quality of voice of an IP telephone, a techniqueof calculating a loss rate of packets per unit time in each of real-timetransport protocol (RTP) sessions has been developed. For example, asillustrated in FIG. 33, an amount (referred to as a receipt count ofpackets) of received packets and an amount (referred to as a loss countof packets) of loss packets per predetermined period of time are countedup, and the loss rate of packets is calculated. Note that in FIG. 33,circles with a solid outline represent received packets, and circleswith a dotted outline represent loss packets. In addition, FIG. 33illustrates a case in which three packets (packets having sequencenumbers of 4, 11, and 15) out of one hundred packets have been lost.Thus, the loss rate of packets is 3.0%. Note that it may be determinedwhether a packet is lost by monitoring the sequence number contained ineach of the packets.

Related techniques are disclosed in Japanese Laid-Open PatentPublication No. 2003-249945 and Japanese Laid-Open Patent PublicationNo. 11-259099.

SUMMARY

According to an aspect of the present invention, provided is a methodexecuted by a packet analysis apparatus for analyzing packets includingvoice packets and non-voice packets. The method includes: capturingpackets in a specific session; storing the captured packets in astorage; screening the stored packets to count up a receipt count ofvoice packets; determining whether packet loss has occurred in thespecific session; and determining whether loss packets are voice packetsin accordance with received packets adjacent to the loss packets tocount up a loss count of voice packets when the packet loss hasoccurred.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an embodiment of the present invention;

FIG. 2 is a diagram illustrating an embodiment of the present invention;

FIG. 3 is a diagram illustrating an example of a system according to anembodiment of the present invention;

FIG. 4 is a diagram illustrating an example of a functionalconfiguration of a packet analysis apparatus according to an embodimentof the present invention;

FIG. 5 is a diagram illustrating an example of data stored in a qualitydata storage according to an embodiment of the present invention;

FIG. 6 is a diagram illustrating an example of an operation flow of anentire process performed by a packet analysis apparatus according to anembodiment of the present invention;

FIG. 7 is a diagram illustrating an example of a data format of an RTPpacket;

FIG. 8 is a diagram illustrating an example of a screen for displaying acalculation result of transmission quality according to an embodiment ofthe present invention;

FIG. 9 is a diagram illustrating an example of log data of transmissionquality according to an embodiment of the present invention;

FIG. 10 is a diagram illustrating an example of a DTMF event;

FIG. 11 is a diagram illustrating an example of information contained inDTMF packets included in a DTMF event;

FIG. 12 is a diagram illustrating an example of an operation flow of aloss packet estimation process according to an embodiment of the presentinvention;

FIG. 13 is a diagram illustrating an example of cases in which a firsthalf or a middle of a DTMF event is lost;

FIG. 14 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 15 is a diagram illustrating an example of an operation flow of aloss packet estimation process according to an embodiment of the presentinvention;

FIG. 16 is a diagram illustrating an example of cases in which losspackets are preceded by a retransmitted packet;

FIG. 17 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 18 is a diagram illustrating an example of an operation flow of aloss packet estimation process according to an embodiment of the presentinvention;

FIG. 19 is a diagram illustrating an example of a case in whichretransmitted packets have been lost;

FIG. 20 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 21 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 22 is a diagram illustrating an example of an operation flow of aloss packet estimation process according to an embodiment of the presentinvention;

FIG. 23 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 24 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 25 is a diagram illustrating an example of an operation flow of aloss packet estimation process according to an embodiment of the presentinvention;

FIG. 26 is a diagram illustrating an example of a loss packet estimationprocess according to an embodiment of the present invention;

FIG. 27 is a diagram illustrating an example of an operation flow of aloss packet estimation process according to an embodiment of the presentinvention;

FIG. 28 is a diagram illustrating an example of a case in which bothprevious and next packets to loss packets are voice packets;

FIG. 29 is a diagram illustrating an example of a case in which bothprevious and next packets to loss packets are DTMF packets;

FIG. 30 is a diagram illustrating an example of a case in which previousand next packets to loss packets are packets of different types;

FIG. 31 is a diagram illustrating an example of an operation flow of aprocess performed by a packet analysis apparatus according to anembodiment of the present invention;

FIG. 32 is a diagram illustrating an example of a functionalconfiguration of a packet analysis apparatus according to an embodimentof the present invention;

FIG. 33 is a diagram illustrating an example of a related technology;and

FIG. 34 is a diagram illustrating an example of a system configurationof a computer.

DESCRIPTION OF EMBODIMENTS

In voice communication using IP telephones, a dual-tone multi frequency(DTMF) signal, which is a non-voice signal, may flow in addition to avoice signal in a network. That is, both a voice signal and a DTMFsignal (i.e., a non-voice signal) may flow in the same RTP session.

However, in the conventional techniques, non-voice signals and voicesignals are analyzed without being separated from each other when thequality of voice is measured. In addition, it may be difficult inconventional techniques to determine whether the loss packets are voicepackets or non-voice packets. That is, in conventional techniques, whenvoice packets and non-voice packets flow in the same RTP session, it isdifficult to measure the transmission quality of voice packets, whichgives an indication of the quality of voice, by substantiallyeliminating the influence of the non-voice packets.

Accordingly, it is preferable to provide a method for measuring thetransmission quality of voice packets by substantially eliminating theinfluence of the non-voice packets.

The outline of embodiments of the present invention will be discussedfirst with reference to FIGS. 1 and 2. FIG. 1 illustrates an example ofa series of packets that flow between IP telephones via a packetcommunication network. FIG. 2 illustrates an example of loss packetestimation. According to the embodiments of the present invention, apacket analysis apparatus captures packets flowing in an RTP session anddetermines, in accordance with the payload type included in the packets,what type of packets the captured packets are. In addition, according tothe embodiments, the packet analysis apparatus determines whether packetloss has occurred and determines the type of loss packets when packetloss has occurred. Sequential sequence numbers are assigned to packetsthat flow in an RTP session. This allows the packet analysis apparatusto determine whether packets have been lost in accordance with thesequence numbers contained in the packets. In this way, for example, asillustrated in FIG. 2, the packet analysis apparatus may count up anamount (referred to as a receipt count of voice packets) of receivedvoice packets and an amount (referred to as a loss count of voicepackets) of voice loss packets and, therefore, the packet analysisapparatus may calculate the loss rate of voice packets by substantiallyeliminating the influence of the non-voice packets. In FIG. 2, threepackets (the packets having sequence numbers of 4, 11, and 15) out ofone hundred packets have been lost. The three loss packets include onevoice packet and two DTMF packets (i.e., non-voice packets).Accordingly, in the example illustrated in FIG. 2, the loss rate ofvoice packets may be calculated as follows:1/(90+1)≈1.1%Note that in FIGS. 1 and 2, circles with a solid outline representreceived packets, and circles with a dotted outline represent losspackets. In addition, circles with a lattice pattern represent voicepackets, and diagonally hatched circles represent DTMF packets (the sameapplies to the subsequent drawings). The embodiments will be discussedin more detail below.

First Embodiment

A first embodiment of the present invention will be discussed next withreference to FIGS. 3 to 14, 31, and 32. FIG. 3 illustrates an example ofa system according to the present embodiment. As illustrated in FIG. 3,networks 3 a, 3 b, and 3 c connect to a packet communication network 1.In addition, an IP telephone and a personal computer (PC) connect torespective networks 3 a, 3 b, and 3 c. For example, voice communicationbetween the IP telephones and data communication between the PCs may beperformed via the networks 3 a, 3 b, and 3 c, and the packetcommunication network 1. As illustrated in FIG. 3, a monitoring point isprovided between the packet communication network 1 and the network 3 a.The network 3 a connects to the packet communication network 1 through atap 5 installed at the monitoring point. Furthermore, a packet analysisapparatus 7 is installed at the monitoring point. The packet analysisapparatus 7 captures, via the tap 5, a packet that passes through themonitoring point. While a single monitoring point is provided in FIG. 3,a plurality of monitoring points may be provided.

FIG. 32 illustrates an example of a functional configuration of thepacket analysis apparatus 7 according to the present embodiment. Asillustrated in FIG. 32, the packet analysis apparatus 7 includes apacket captor 3201 for capturing packets, a voice packet screener 3203for screening voice packets, a loss packet estimator 3205 for countingan amount of voice loss packets, and a storage 3207 for storing capturedpackets and other data. FIG. 31 illustrates an operation flow of aprocess performed by the packet analysis apparatus 7 according to thepresent embodiment.

In operation S101, the packet captor 3201 captures packets.

In operation S103, the voice packet screener 3203 counts up receiptcount of voice packets.

In operation S105, the loss packet estimator 3205 determines whetherpacket loss has occurred.

In operation S107, the loss packet estimator 3205 counts up loss countof voice packets.

FIG. 4 illustrates an example of a detailed functional configuration ofthe packet analysis apparatus 7 according to the present embodiment. InFIG. 4, the packet analysis apparatus 7 includes a packet captor 71, apacket analyzer 72, a voice packet screener 73, a loss packet estimator74, a quality calculator 75, an output unit 76, and a quality datastorage 77.

The packet captor 71 captures, using the tap 5, a packet that flowsthrough the monitoring point and outputs the captured packet to thepacket analyzer 72. Upon receiving the packet from the packet captor 71,the packet analyzer 72 analyzes the header of the packet to determinewhether the packet is an RTP packet. When the packet is an RTP packet,the packet analyzer 72 stores the RTP packet in a storage unit (notillustrated). The packet analyzer 72 instructs the voice packet screener73 to determine whether the stored packets are voice packets or DTMFpackets. Upon receiving the instruction from the packet analyzer 72, thevoice packet screener 73 determines whether each of the packets storedin the storage unit is a voice packet or a DTMF packet in accordancewith the payload type included in the header of the packet and counts upa receipt count of voice packets and an amount (referred to as a receiptcount of DTMF packets) of received DTMF packets. The voice packetscreener 73 stores the receipt count of voice packets and the receiptcount of DTMF packets in the quality data storage 77. In addition, thevoice packet screener 73 instructs the loss packet estimator 74 to starta loss packet estimation process discussed below. Upon receiving theinstruction from the voice packet screener 73, the loss packet estimator74 determines whether packet loss has been occurred in accordance withthe packets stored in the storage unit. Upon determining that packetloss has been occurred, the loss packet estimator 74 performs the losspacket estimation process to count up a loss count of voice packets andan amount (referred to as a loss count of DTMF packets) of DTMF losspackets respectively. The loss packet estimator 74 stores the loss countof voice packets and the loss count of DTMF packets in the quality datastorage 77. Furthermore, the loss packet estimator 74 instructs thequality calculator 75 to calculate the transmission quality in terms ofa loss rate of packets and an arrival rate of packets, for example. Uponreceiving the instruction from the loss packet estimator 74, the qualitycalculator 75 calculates the transmission quality of voice packets andDTMF packets in accordance with the receipt count of packets and theloss count of packets stored in the quality data storage 77 and storesthe calculated transmission quality of voice packets and DTMF packets inthe quality data storage 77. In addition, the quality calculator 75instructs the output unit 76 to output the quality data stored in thequality data storage 77. Upon receiving the instruction from the qualitycalculator 75, the output unit 76 generates output data in accordancewith the data stored in the quality data storage 77 to display theoutput data on a display unit or transmits the output data to a userterminal (not illustrated).

FIG. 5 illustrates an example of data stored in the quality data storage77 according to the present embodiment. In the example illustrated inFIG. 5, the quality data storage 77 stores respective receipt counts,loss counts, and loss rates of voice packets and DTMF packets. Thequality data storage 77 may further store respective arrival rates ofvoice packets and DTMF packets, and an amount (referred to as a losscount of unknown packets) of unknown loss packets. The quality datastorage 77 stores the data illustrated in FIG. 5 for each of RTPsessions. If the transmission quality is measured at predetermined timeintervals, the quality data storage 77 may store the quality data foreach of the time intervals. In the present embodiment, the quality datastorage 77 stores not only data on voice packets but also data on allpackets, data on DTMF packets, and data on unknown packets. However, thequality data storage 77 may store only data on voice packets.Alternatively, the quality data storage 77 may store data on voicepackets and only one of data on all packets, data on DTMF packets, anddata on unknown packets. This also applies to other embodiments.

An example of a process performed by the packet analysis apparatus 7according to the first embodiment will be discussed next with referenceto FIGS. 6 to 14. FIG. 6 illustrates an example of an operation flow ofan entire process performed by the packet analysis apparatus 7 accordingto the present embodiment.

In operation S1, the packet captor 71 captures, using the tap 5, apacket that flows in the network and outputs the captured packet to thepacket analyzer 72.

In operation S3, upon receiving the packet from the packet captor 71,the packet analyzer 72 determines whether the packet is an RTP packet.When the packet is an RTP packet, the packet analyzer 72 stores the RTPpacket in the storage unit. The packet analyzer 72 instructs, atpredetermined time intervals or at any time, the voice packet screener73 to determine whether the stored packets are voice packets or DTMFpackets. For example, if it is decided in advance that the transmissionquality is to be measured at certain time intervals, the packet analyzer72 sends the instruction at the certain time intervals.

In operation S5, upon receiving the instruction from the packet analyzer72, the voice packet screener 73 determines whether each of the RTPpackets stored in the storage unit is a voice packet or a DTMF packet inaccordance with the payload type included in the header of the RTPpacket and counts up a receipt count of voice packets and a receiptcount of DTMF packets. The voice packet screener 73 stores the receiptcount of voice packets and the receipt count of DTMF packets in thequality data storage 77. If, for example, it is decided in advance thatthe transmission quality is to be measured at certain time intervals,the voice packet screener 73 makes determination for packets capturedafter the previous determination and counts up the receipt count ofpackets.

FIG. 7 illustrates an example of a data format of an RTP packet. The RTPpacket illustrated in FIG. 7 is a DTMF packet. As illustrated in FIG. 7,the RTP packet includes an RTP header and an RTP payload. The RTP headerincludes a marker (M) bit, a payload type, a sequence number, and a timestamp. The RTP payload includes an event number, an end (E) bit, and aduration. Note that, only data items relating to the process accordingto the present embodiment are illustrated in FIG. 7. Since the RTPpacket is the same as a conventional RTP packet, detailed discussionthereof will be omitted.

The voice packet screener 73 instructs the loss packet estimator 74 tostart a loss packet estimation process.

In operation S7, upon receiving the instruction from the voice packetscreener 73, the loss packet estimator 74 determines whether packet losshas been occurred in accordance with the sequence numbers of the packetsstored in the storage unit.

In operation S9, when the loss packet estimator 74 has detected packetloss (“Yes” in operation S7), the loss packet estimator 74 performs aloss packet estimation process in accordance with the packets stored inthe storage unit. The loss packet estimation process will be discussedlater in more detail. By performing the loss packet estimation process,the loss packet estimator 74 counts up a loss count of voice packets anda loss count of DTMF packets and stores the loss count of voice packetsand the loss count of DTMF packets in the quality data storage 77. Uponcompleting the loss packet estimation process, the loss packet estimator74 instructs the quality calculator 75 to calculate the transmissionquality in terms of a loss rate of packets and an arrival rate ofpackets, for example. Thereafter, the packet analysis apparatus 7advances the process to operation S11.

When the loss packet estimator 74 has not detected packet loss (“No” inoperation S7), the packet analysis apparatus 7 skips operation S9 andadvances the process to operation S11. The loss packet estimator 74instructs the quality calculator 75 to calculate the transmissionquality in terms of a loss rate of packets and an arrival rate ofpackets, for example.

In operation S11, upon receiving the instruction from the loss packetestimator 74, the quality calculator 75 calculate the transmissionquality in terms of a loss rate of packets and an arrival rate ofpackets in accordance with the receipt count of packets and the losscount of packets stored in the quality data storage 77 and stores thecalculated transmission quality in the quality data storage 77. Forexample, when the receipt count of packets and the loss count of packetsstored in the quality data storage 77 are as illustrated in FIG. 5, theloss rate of voice packets is calculated as follows: 1/(90+1)≈1.1%, andthe loss rate of DTMF packets is calculated as follows: 2/(7+2)≈22.2%.When the loss rate of packets in whole and the arrival rate of packetsin whole are needed, the quality calculator 75 calculates the loss rateof packets in whole and the arrival rate of packets in whole, and storesthe rates in the quality data storage 77. If it is decided in advancethat the transmission quality is to be measured at certain timeintervals, the quality calculator 75 may calculate an average value ofthe loss rates of packets and an average value of the arrival rates ofpackets. Thereafter, the quality calculator 75 instructs the output unit76 to output the quality data stored in the quality data storage 77.

In operation S13, upon receiving the instruction from the qualitycalculator 75, the output unit 76 generates, in accordance with the datastored in the quality data storage 77, screen data representing thecalculation result of the transmission quality and displays the screendata on, for example, a display unit. FIG. 8 illustrates an example of ascreen for displaying a calculation result of transmission qualityaccording to the present embodiment. The screen illustrated in FIG. 8 isdisplayed, for example. In the screen for displaying the calculationresult of the transmission quality illustrated in FIG. 8, the totalcount of loss packets, the loss rate of packets in whole, the loss countof voice packets, the loss rate of voice packets, the loss count of DTMFpackets, and the loss rate of DTMF packets are displayed. Although notillustrated in FIG. 8, the loss count of unknown packets may bedisplayed. According to the present embodiment, in addition to data onvoice packets, data on all packets and DTMF packets are displayed on thescreen for displaying the calculation result of the transmissionquality. However, only data on voice packets may be displayed.Alternatively, data on voice packets and only one of data on allpackets, data on DTMF packets, and data on unknown packets may bedisplayed. This also applies to other embodiments.

If it is determined in advance that the transmission quality is to bemeasured at certain time intervals, the quality calculator 75 maygenerate log data of the measured transmission quality and store thegenerated log data in the quality data storage 77. FIG. 9 illustrates anexample of log data of transmission quality according to the presentembodiment. The example of log data illustrated in FIG. 9 includes dataon loss packets in whole, data on voice loss packets, data on DTMF losspackets, and data on unknown loss packets. The data on loss packets inwhole includes the loss count (“loss-packet” in FIG. 9) of packets, thereceipt count (“recv-packet” in FIG. 9) of packets, the maximum(“loss-rate-max” in FIG. 9) of the measured loss rates, the minimum(“loss-rate-min” in FIG. 9) of the measured loss rates, and the average(“loss-rate-avg” in FIG. 9) of the measured loss rates. The data onvoice loss packets includes the receipt count (“voice-recv-packet” inFIG. 9) of voice packets, the loss count (“voice-loss-packet” in FIG. 9)of voice packets, the maximum (“voice-loss-rate-max” in FIG. 9) of themeasured voice loss rates, the minimum (“voice-loss-rate-min” in FIG. 9)of the measured voice loss rates, and the average (“voice-loss-rate-avg”in FIG. 9) of the measured voice loss rates. The data on DTMF losspackets includes the receipt count (“dtmf-recv-packet” in FIG. 9) ofDTMF packets, the loss count (“dtmf-loss-packet”in FIG. 9) of DTMFpackets, the maximum (“dtmf-loss-rate-max” in FIG. 9) of the measuredDTMF loss rates, the minimum (“dtmf-loss-rate-min” in FIG. 9) of themeasured DTMF loss rates, and the average (“dtmf-loss-rate-avg” in FIG.9) of the measured DTMF loss rates. The data on unknown loss packetsincludes the loss count (“unknown-loss-packet” in FIG. 9) of unknownpackets.

An example (referred to as a first loss packet estimation process) of aloss packet estimation process performed in operation S9 illustrated inFIG. 6 will be discussed next with reference to FIGS. 10 to 14. Beforediscussing the operation flow in detail, a DTMF event and a DTMF packetwill be discussed. A DTMF event is generated for each of push tones andincludes a plurality of DTMF packets. FIG. 10 illustrates a DTMF eventgenerated when a button “5” is pressed. FIG. 11 illustrates informationcontained in each of six DTMF packets illustrated in FIG. 10. In a DTMFsignaling, as illustrated in FIG. 10, a terminal packet is retransmittedtwice. A series of DTMF packets (six DTMF packets in FIG. 10) includingthe packets (hereinafter referred to as retransmitted packets) to beretransmitted form a DTMF event. Note that, in FIG. 10, diagonallyhatched circles with a letter “R” represent retransmitted packets (thesame applies to the subsequent drawings). The end (E) bit of theretransmitted packet is always set to “1”. The value for the duration ofthe retransmitted packet is set to the value for the duration of theterminal packet, as illustrated in FIGS. 10 and 11. The duration is anelapsed time measured from when the push button is pressed and isrepresented by a time stamp. Under such definitions, the first losspacket estimation process according to the present embodiment will bediscussed in detail with reference to FIG. 12. FIG. 12 illustrates anoperation flow of the first loss packet estimation process according tothe present embodiment.

In operation S21, the loss packet estimator 74 determines, in accordancewith the packets stored in the storage unit, whether there are losspackets succeeded by a retransmitted packet or by a group of DTMFpackets including a retransmitted packet. That is, the loss packetestimator 74 determines whether the first half or the middle of the DTMFevent is lost. The determination is made in accordance with the payloadtype, the end (E) bit, and the duration of each of the packet stored inthe storage unit.

FIG. 13 illustrates cases in which a first half or a middle of a DTMFevent has been lost. Note that in each of the cases illustrated in FIG.13, the sequence numbers are assigned to the DTMF packets in ascendingorder from right to left. In case C1, there are loss packets succeededby three DTMF packets (two of them are retransmitted packets) andpreceded by a voice packet. In case C2, there are loss packets succeededby two retransmitted packets and preceded by a voice packet. In case C3,there are loss packets succeeded by one retransmitted packet andpreceded by a voice packet. In case C4, there are loss packets succeededby three DTMF packets (two of them are retransmitted packets) andpreceded by a DTMF packet. In case C5, there are loss packets succeededby two retransmitted packets and preceded by a DTMF packet. In case C6,there are loss packets succeeded by one retransmitted packet andpreceded by a DTMF packet.

When there is no loss packet succeeded by a retransmitted packet or by agroup of DTMF packets including a retransmitted packet (“No” inoperation S21), the loss packet estimator 74 terminates the first losspacket estimation process, and returns to the original processillustrated in FIG. 6.

In operation S23, when there are loss packets succeeded by aretransmitted packet or by a group of DTMF packets including aretransmitted packet (“Yes” in operation S21), the loss packet estimator74 obtains the duration included in the payload of the retransmittedpacket. FIG. 14 illustrates an example of the first loss packetestimation process according to the present embodiment. Operation S23and subsequent operations will be discussed with reference to a specificexample illustrated in FIG. 14. FIG. 14 illustrates five loss packetssucceeded by four DTMF packets and preceded by a voice packet. Note thatin FIG. 14, the sequence numbers are assigned to the DTMF packets inascending order from right to left. In the example illustrated in FIG.14, a value “640” is obtained as the duration of the retransmittedpackets in operation S23. As mentioned earlier, the duration isrepresented by a time stamp.

In operation S25, the loss packet estimator 74 obtains a transmissioninterval of DTMF packets. More specifically, the loss packet estimator74 obtains a difference, as the transmission interval, between theduration of the DTMF packet succeeding the loss packets and the durationof the next DTMF packet (i.e., the terminal packet in FIG. 14). In theexample illustrated in FIG. 14, the duration of the DTMF packetsucceeding the loss packets is 480, and the duration of the next DTMFpacket is 640. Thus, a difference of 160 is obtained as the transmissioninterval in operation S25.

DTMF packets that flow in the same RTP session are transmitted atconstant time intervals. Accordingly, for example, in a RTP session, aDTMF event that normally flows may be detected, and a difference betweenthe durations of two neighboring DTMF packets in the DTMF event may beobtained as the transmission interval.

In operation S27, the loss packet estimator 74 calculates a total countof packets from the lead packet to the terminal packet in accordancewith the duration obtained in operation S23 and the transmissioninterval obtained in operation S25. More specifically, the loss packetestimator 74 divides the duration by the transmission interval to obtainthe total count of packets. In the example illustrated in FIG. 14, thetotal count of packets is calculated as follows: 640/160=4.

In operation S29, the loss packet estimator 74 determines the type ofloss packets in accordance with the total count of packets calculated inoperation S27, an amount of DTMF packets succeeding the loss packets,and a retransmission count of the terminal packet to count up the losscount of voice packets and the loss count of DTMF packets. Morespecifically, the loss packet estimator 74 determines the location ofthe terminal packet in accordance with the amount of DTMF packetssucceeding the loss packets and the retransmission count of the terminalpacket. In the example illustrated in FIG. 14, among four DTMF packetssucceeding the loss packets, the second packet from the top isdetermined to be the terminal packet. Thereafter, the loss packetestimator 74 determines the location of the lead packet in accordancewith the total count of packets calculated in operation S27. In theexample illustrated in FIG. 14, among five loss packets, the fourthpacket from the top is determined to be the lead packet. Accordingly, inFIG. 14, it is determined that, among the five loss packets, the lasttwo packets are DTMF packets, and the first three packets are voicepackets. The loss count of voice packets and the loss count of DTMFpackets are stored in the quality data storage 77. Thereafter, the losspacket estimator 74 terminates the first loss packet estimation process,and returns to the original process illustrated in FIG. 6.

When packet loss occurred at a plurality of locations, theabove-discussed process is performed for each of the locations, and thetotal loss count of packets is stored in the quality data storage 77.

Thus, the type of loss packets may be determined when the first half orthe middle of the DTMF event may possibly be lost.

Second Embodiment

A second embodiment of the present invention will be discussed next withreference to FIGS. 15 to 17. The second embodiment discusses a techniquefor determining the type of loss packets when the last half of the DTMFevent may possibly be lost.

The system configuration of the second embodiment is similar to thatillustrated in FIG. 3. In addition, the functional configuration of thepacket analysis apparatus 7 according to the second embodiment issimilar to that illustrated in FIG. 4. FIG. 15 illustrates an operationflow of a loss packet estimation process according to the secondembodiment. The process performed by the packet analysis apparatus 7 isbasically similar to that discussed in the first embodiment. However, inplace of the first loss packet estimation process performed in operationS9 in FIG. 6, a process (referred to as a second loss packet estimationprocess) as illustrated in FIG. 15 is performed. The second loss packetestimation process will be discussed below.

In operation S31, the loss packet estimator 74 determines, in accordancewith packets stored in the storage unit, whether there are loss packetspreceded by a retransmitted packet. That is, it is determined whether alast half of the DTMF event may possibly be lost.

FIG. 16 illustrates cases in which the loss packets are preceded by aretransmitted packet. Note that in each of the cases illustrated in FIG.16, the sequence numbers are assigned to the DTMF packets in ascendingorder from right to left. In case C7, the loss packets are succeeded bya voice packet and preceded by one retransmitted packet. In case C8, theloss packets are succeeded by a voice packet and preceded by tworetransmitted packets.

When there is no loss packet preceded by a retransmitted packet (“No” inoperation S31), the loss packet estimator 74 terminates the second losspacket estimation process, and returns to the original processillustrated in FIG. 6.

In operation S33, when there are loss packets preceded by aretransmitted packet (“Yes” in operation S31), the loss packet estimator74 obtains the duration included in the retransmitted packet todetermine the location of the terminal packet in accordance with theduration. Operation S33 and the subsequent operation will be discussedwith reference to a specific example illustrated in FIG. 17. FIG. 17illustrates an example of the second loss packet estimation processaccording to the present embodiment, in which five loss packets aresucceeded by a voice packet and preceded by one retransmitted packet.Note that in FIG. 17, the sequence numbers are assigned to the DTMFpackets in ascending order from right to left. As mentioned earlier, theduration of the retransmitted packet is set to a value that is identicalwith that of the terminal packet. Accordingly, among DTMF packets havinga duration that is identical with that of the retransmitted packet, theloss packet estimator 74 determines a DTMF packet having the minimumsequence number as the terminal packet. In FIG. 17, among the five DTMFpackets preceding the loss packets, the fourth packet from the top isdetermined to be the terminal packet.

In operation S35, the loss packet estimator 74 determines the type ofloss packets in accordance with the location of the terminal packet andthe retransmission count of the terminal packet and counts up a losscount of voice packets and a loss count of DTMF packets. In the exampleillustrated in FIG. 17, there is only one retransmitted packet, althoughtwo retransmitted packets are supposed to. Accordingly, it may bedetermined that one retransmitted packet has been lost. That is, in FIG.17, it is determined that, among the five loss packets, the first packetis a DTMF packet and the other four packets are voice packets. The losscount of voice packets and the loss count of DTMF packets are stored inthe quality data storage 77. Thereafter, the loss packet estimator 74terminates the second loss packet estimation process, and returns to theoriginal process illustrated in FIG. 6.

Thus, the type of loss packets may be determined when the last half ofthe DTMF event may possibly be lost.

Third Embodiment

A third embodiment of the present invention will be discussed next withreference to FIGS. 18 to 21. The third embodiment discusses a techniquefor determining the type of some of the loss packets when theretransmitted packets have been lost.

The system configuration of the third embodiment is similar to thatillustrated in FIG. 3. In addition, the functional configuration of apacket analysis apparatus 7 according to the third embodiment is similarto that illustrated in FIG. 4. FIG. 18 illustrates an operation flow ofa loss packet estimation process according to the third embodiment. Theprocess performed by the packet analysis apparatus 7 is basicallysimilar to that discussed in the first embodiment. However, in place ofthe first loss packet estimation process performed in operation S9illustrated in FIG. 6, a process (referred to as a third loss packetestimation process) as illustrated in FIG. 18 is performed. The thirdloss packet estimation process will be discussed below.

In operation S41, the loss packet estimator 74 determines whether theretransmitted packets have been lost in accordance with the packetsstored in the storage unit. More specifically, the loss packet estimator74 determines whether there are loss packets succeeded by a voice packetand preceded by a DTMF packet other than a retransmitted packet.

FIG. 19 illustrates a case in which retransmitted packets have beenlost. Note that in case C9 illustrated in FIG. 19, the sequence numbersare assigned to the DTMF packets in ascending order from right to left.In case C9, the loss packets are succeeded by a voice packet andpreceded by a DTMF packet other than a retransmitted packet.

When the retransmitted packets have not been lost (“No” in operationS41), the loss packet estimator 74 terminates the third loss packetestimation process, and returns to the original process illustrated inFIG. 6.

In operation S43, when the retransmitted packets have been lost (“Yes”in operation S41), the loss packet estimator 74 counts up the loss countof DTMF packets by the retransmission count of the terminal packet andcounts up the loss count of voice packets (or unknown packets) by adifference between the loss count of packets and the loss count of DTMFpackets thereof. Note that since the retransmitted packets have beenlost, at least DTMF packets of the retransmission count have been lost.That is, in operation S43, the loss packet estimator 74 counts up theloss count of DTMF packets by the retransmission count of the terminalpacket and counts up the loss count of voice packets (or unknownpackets) by the amount of other loss packets. FIGS. 20 and 21 illustratean example of the third loss packet estimation process according to thepresent embodiment, in which five loss packets include the retransmittedpackets. When packets have been lost as in case C9 illustrated in FIG.19, the loss count of DTMF packets is 2, and the loss count of voicepackets (or unknown packets) is 3, as illustrated in FIG. 20. The losscount of voice packets, the loss count of DTMF packets, and the losscount of unknown packets are stored in the quality data storage 77.Thereafter, the loss packet estimator 74 terminates the third losspacket estimation process, and returns to the original processillustrated in FIG. 6.

When packets have been lost as in case C9 illustrated in FIG. 19, theloss packets may be in one of four patterns illustrated in FIG. 21. Inthis case, the maximum loss count of voice packets is 3 and the minimumloss count of voice packets is 0. Accordingly, the loss count of voicepackets may be counted in a range. In such a case, the transmissionquality in the case of the maximum loss count and the transmissionquality in the case of the minimum loss count may be calculated andoutput.

Thus, the type of at least some of the loss packets may be determinedwhen the retransmitted packets have been lost, and the range of the lossrate of voice packets may be determined.

Fourth Embodiment

A fourth embodiment according to the present invention will be discussednext with reference to FIGS. 22 to 24. The fourth embodiment discusses atechnique for determining the type of loss packets when the transmissioninterval of voice packets differs from that of DTMF packets. Assume, inthe present embodiment, that the transmission interval of voice packetsis 20 ms, and that the transmission interval of DTMF packets is 40 ms.

The system configuration of the fourth embodiment is similar to thatillustrated in FIG. 3. In addition, the functional configuration of apacket analysis apparatus 7 according to the fourth embodiment issimilar to that illustrated in FIG. 4. FIG. 22 illustrates an operationflow of a loss packet estimation process according to the fourthembodiment. The process performed by the packet analysis apparatus 7 isbasically similar to that discussed in the first embodiment. However, inplace of the first loss packet estimation process performed in operationS9 illustrated in FIG. 6, a process (referred to as a fourth loss packetestimation process) as illustrated in FIG. 22 is performed. The fourthloss packet estimation process will be discussed below.

In operation S51, the loss packet estimator 74 determines whether thetransmission interval of voice packets differs from the transmissioninterval of DTMF packets. The transmission interval of voice packets andthe transmission interval of DTMF packets may be calculated inaccordance with, for example, captured packets. When the transmissioninterval of voice packets is identical with that of DTMF packets (“No”in operation S51), the loss packet estimator 74 terminates the fourthloss packet estimation process, and returns to the original processillustrated in FIG. 6.

In operation S53, when the transmission interval of voice packetsdiffers from the transmission interval of DTMF packets (“Yes” inoperation S51), the loss packet estimator 74 calculates a difference intime and the sequence number between the previous and next packets tothe loss packets. The “previous and next packets” refers to a packethaving a sequence number that indicates the location preceding the losspackets and a packet having a sequence number that indicates thelocation succeeding the loss packets, respectively. The difference intime between the previous and next packets to the loss packets may beobtained by calculating a difference between the time stamps included inthe header of the previous and next packets and converting thedifference into an actual period of time.

In operation S55, the loss packet estimator 74 calculates thetransmission interval of loss packets in accordance with the differencein time and the sequence number calculated in operation S53. Morespecifically, the loss packet estimator 74 divides the difference intime by the difference in the sequence number to calculate thetransmission interval of loss packets.

FIG. 23 illustrates an example of the fourth loss packet estimationprocess according to the present embodiment, in which seven voicepackets, for example, have been lost. In the example illustrated in FIG.23, the difference in time between the previous and next packets to theloss packets is 160 ms, and the difference in the sequence number is 8(=13−5). Accordingly, the transmission interval of loss packets iscalculated as follows: 160 ms/8=20 ms.

In operation S57, the loss packet estimator 74 determines whether thetransmission interval of loss packets is identical with that of voicepackets.

In operation S59, when the transmission interval of loss packets isidentical with that of voice packets (“Yes” in operation S57), the losspacket estimator 74 determines that all of the loss packets are voicepackets. Thus, the loss packet estimator 74 counts up the loss count ofvoice packets by the loss count of packets. In the example illustratedin FIG. 23, it is determined that the transmission interval of losspackets (20 ms) is identical with that of voice packets (20 ms). Thus,the loss packet estimator 74 counts up the loss count of voice packetsby the loss count of packets (7). The loss count of voice packets isstored in the quality data storage 77. Thereafter, the loss packetestimator 74 terminates the fourth loss packet estimation process, andreturns to the original process illustrated in FIG. 6.

In operation S61, when the transmission interval of loss packets differsfrom that of voice packets (“No” in operation S57), the loss packetestimator 74 determines that DTMF packets have been lost.

FIG. 24 illustrates an example of the fourth loss packet estimationprocess according to the present embodiment, in which four DTMF packets,for example, have been lost. In the example illustrated in FIG. 24, thedifference in time between the previous and next packets to the losspackets is 180 ms, and the difference in the sequence number is 5(=10−5). In this case, the transmission interval of loss packets iscalculated, in operation S55, as follows: (180 ms−20 ms)/(5−1)=40 ms.That is, it is determined, in operation S57, that the transmissioninterval of loss packets (40 ms) differs from that of voice packets (20ms) and, therefore, it is determined, in operation S61, that DTMFpackets have been lost.

In operation S63, the loss packet estimator 74 determines whether thetransmission interval of loss packets is identical with that of DTMFpackets.

In operation S65, when the transmission interval of loss packets isidentical with that of DTMF packets (“Yes” in operation S63), the losspacket estimator 74 determines that all of the loss packets are DTMFpackets, that is, the loss packet estimator 74 determines that no voicepackets have been lost. Thus, the loss packet estimator 74 counts up theloss count of DTMF packets by the loss count of packets. The loss countof voice packets (=0) calculated in accordance with the loss count ofDTMF packets is stored in the quality data storage 77. Alternatively,the loss count of voice packets may not be stored in the quality datastorage 77 since the loss count of voice packets is 0. Thereafter, theloss packet estimator 74 terminates the fourth loss packet estimationprocess, and returns to the original process illustrated in FIG. 6.

When the transmission interval of loss packets differs from that of DTMFpackets (“No” in operation S63), operation S65 is skipped. Thereafter,the loss packet estimator 74 terminates the fourth loss packetestimation process, and returns to the original process illustrated inFIG. 6.

Thus, the type of loss packets may be determined when the transmissioninterval of voice packets differs from that of DTMF packets.

Fifth Embodiment

A fifth embodiment according to the present invention will be discussednext with reference to FIGS. 25 and 26. The fifth embodiment discusses atechnique for calculating the loss count of voice packets and the losscount of DTMF packets when the transmission interval of voice packetsdiffers from that of DTMF packets. Assume, in the present embodiment,that the transmission interval of voice packets is 20 ms, and that thetransmission interval of DTMF packets is 40 ms.

The system configuration of the fifth embodiment is similar to thatillustrated in FIG. 3. In addition, the functional configuration of apacket analysis apparatus 7 according to the fifth embodiment is similarto that illustrated in FIG. 4. FIG. 25 illustrates an operation flow ofa loss packet estimation process according to the fifth embodiment. Theprocess performed by the packet analysis apparatus 7 is basicallysimilar to that discussed in the first embodiment. However, in place ofthe first loss packet estimation process performed in operation S9illustrated in FIG. 6, a process (referred to as a fifth loss packetestimation process) as illustrated in FIG. 25 is performed. The fifthloss packet estimation process will be discussed below.

In operation S71, the loss packet estimator 74 determines whether thetransmission interval of voice packets differs from the transmissioninterval of DTMF packets. When the transmission interval of voicepackets is identical with that of DTMF packets (“No” in operation S71),the loss packet estimator 74 terminates the fifth loss packet estimationprocess, and returns to the original process illustrated in FIG. 6.

In operation S73, when the transmission interval of voice packetsdiffers from the transmission interval of DTMF packets (“Yes” inoperation S71), the loss packet estimator 74 calculates a difference intime and the sequence number between the previous and next packets tothe loss packets. Operation S73 and the subsequent operation will bediscussed with reference to an example illustrated in FIG. 26. FIG. 26illustrates an example of the fifth loss packet estimation processaccording to the present embodiment, in which six packets (two voicepackets and four DTMF packets) have been lost. In the exampleillustrated in FIG. 26, the difference in time between the previous andnext packets to the loss packets is 220 ms, and the difference in thesequence number is 7 (=10−3).

In operation S75, the loss packet estimator 74 calculates the loss countof voice packets and the loss count of DTMF packets in accordance withthe transmission interval of voice packets, the transmission interval ofDTMF packets, and the difference in time and the sequence number betweenthe previous and next packets to the loss packets calculated inoperation S73. More specifically, the loss packet estimator 74 performsthe following calculation in accordance with the loss packets and thenext packet to the loss packets. Let x denote a variable indicating anamount of voice packets among the packets, and let y denote a variableindicating an amount of DTMF packets. Then, the values of x and y may beobtained by solving the following simultaneous equations:20x+40y=220  (1)x+y=7  (2)Note that such calculation is performed on seven packets having sequencenumbers of 4 to 10 illustrated in FIG. 26.

Note that in equation (1), “20” represents the transmission interval ofvoice packets, and “40” represents the transmission interval of DTMFpackets. Furthermore, in equation (1), “220” represents the differencein time between the previous and next packets to the loss packetscalculated in operation S73. In equation (2), “7” represents thedifference in the sequence number between the previous and next packetsto the loss packets calculated in operation S73. By solving thesimultaneous equations, the loss packet estimator 74 may obtain asolution: x=3 and y=4. Since the voice packet succeeding the losspackets is included in the calculation, the loss count of voice packetsis the value of x minus one. Accordingly, the loss packets include 2(=3−1) voice packets and 4 DTMF packets. The loss count of voice packetsand the loss count of DTMF packets are stored in the quality datastorage 77. Thereafter, the loss packet estimator 74 terminates thefifth loss packet estimation process, and returns to the originalprocess illustrated in FIG. 6.

Thus, the loss count of voice packets and the loss count of DTMF packetsmay be determined when the transmission interval of voice packetsdiffers from that of DTMF packets.

Sixth Embodiment

A sixth embodiment according to the present invention will be discussednext with reference to FIGS. 27 to 30. Note that the first to fifthembodiments discuss techniques for determining the type of loss packetsusing the above-discussed characteristics of DTMF packets. However,according to the sixth embodiment, the type of loss packets isdetermined in accordance with the type of previous and next packets tothe loss packets.

The system configuration of the sixth embodiment is similar to thatillustrated in FIG. 3. In addition, the functional configuration of apacket analysis apparatus 7 according to the sixth embodiment is similarto that illustrated in FIG. 4. FIG. 27 illustrates an operation flow ofa loss packet estimation process according to the sixth embodiment. Theprocess performed by the packet analysis apparatus 7 is basicallysimilar to that discussed in the first embodiment. However, in place ofthe first loss packet estimation process performed in operation S9illustrated in FIG. 6, a process (referred to as a sixth loss packetestimation process) as illustrated in FIG. 27 is performed. The sixthloss packet estimation process will be discussed below.

In operation S81, the loss packet estimator 74 determines the type ofprevious and next packets to the loss packets in accordance with thepackets stored in the storage unit.

In operation S83, the loss packet estimator 74 determines whether boththe previous and next packets to the loss packets are voice packets.

In operation S85, when both the previous and next packets to the losspackets are voice packets (“Yes” in operation S83), the loss packetestimator 74 determines that all of the loss packets are voice packets.FIG. 28 illustrates an example of the sixth loss packet estimationprocess according to the present embodiment, in which both the previousand next packets to the loss packets are voice packets. In the presentembodiment, the loss packet estimator 74 determines that three losspackets illustrated in FIG. 28 are all voice packets.

The loss packet estimator 74 counts up the loss count of voice packetsby the amount of the loss packets. The loss count of voice packets isstored in the quality data storage 77. Thereafter, the loss packetestimator 74 terminates the sixth loss packet estimation process, andreturns to the original process illustrated in FIG. 6.

In operation S87, when at least one of the previous and next packets tothe loss packets is a DTMF packet (“No” in operation S83), the losspacket estimator 74 determines whether both the previous and nextpackets to the loss packets are DTMF packets.

In operation S89, when both the previous and next packets to the losspackets are DTMF packets (“Yes” in operation S87), the loss packetestimator 74 determines that all of the loss packets are DTMF packets.FIG. 29 illustrates an example of the sixth loss packet estimationprocess according to the present embodiment, in which both the previousand next packets to the loss packets are DTMF packets. In the presentembodiment, the loss packet estimator 74 determines that three losspackets illustrated in FIG. 29 are all DTMF packets.

The loss packet estimator 74 counts up the loss count of DTMF packets bythe amount of the loss packets. The loss count of voice packets (=0)calculated in accordance with the loss count of DTMF packets is storedin the quality data storage 77. Alternatively, the loss count of voicepackets may not be stored in the quality data storage 77 since the losscount of voice packets is 0. Thereafter, the loss packet estimator 74terminates the sixth loss packet estimation process, and returns to theoriginal process illustrated in FIG. 6.

In operation S91, when the type of previous and next packets to the losspackets differs from each other (“No” in operation S87), the loss packetestimator 74 counts up the loss count of unknown packets. FIG. 30illustrates an example of the sixth loss packet estimation processaccording to the present embodiment, in which one of the previous andnext packets to the loss packets is a voice packet and the other is aDTMF packet. In the present embodiment, the loss packet estimator 74determines that three loss packets illustrated in FIG. 30 are allunknown packets. The loss count of voice packets (=0) calculated inaccordance with the loss count of unknown packets is stored in thequality data storage 77. Alternatively, the loss count of voice packetsmay not be stored in the quality data storage 77 since the loss count ofvoice packets is 0. Thereafter, the loss packet estimator 74 terminatesthe sixth loss packet estimation process, and returns to the originalprocess illustrated in FIG. 6.

Thus, the type of loss packets may be determined in accordance with thetype of previous and next packets to the loss packets.

When the type of previous and next packets to the loss packets differsfrom each other, the process discussed in the first to fifth embodimentsmay be employed in place of operation S91.

While embodiments of the present invention have been discussed above,embodiments of the present invention are not limited thereto. Forexample, any of the above-discussed embodiments may be combined.

It should be noted that the above-discussed functional configuration ofthe packet analysis apparatus 7 does not necessarily correspond to anactual program configuration.

The data stored in the quality data storage 77 illustrated in FIG. 5 areonly examples, and the data configurations are not limited to theabove-discussed configuration. In the above-discussed operation flows,the operations may be executed in different order or in parallel if theresults are the same.

The packet analysis apparatus 7 discussed above may be a computer. FIG.34 illustrates an example of a system configuration of a computer. InFIG. 34, a memory 2501, a central processing unit (CPU) 2503, a harddisk drive (HDD) 2505, a display controller 2507 connected to a displayunit 2509, a drive unit 2513 for a computer-readable removable disk2511, an input device 2515, and a communication controller 2517 forconnecting the packet analysis apparatus 7 to a network are connected toone another via a bus 2519. An operating system (OS) and applicationprograms for executing the processes according to the embodiments arestored in the HDD 2505. When the programs are executed by the CPU 2503,the programs are loaded from the HDD 2505 into the memory 2501. In orderto perform necessary operations, the CPU 2503 controls the displaycontroller 2507, the communication controller 2517, and the drive unit2513 as needed. In addition, data being processed is stored in thememory 2501 and is stored in the HDD 2505 as needed. According to theembodiments of the present invention, the application programs thatrealize the above-discussed process are recorded in thecomputer-readable removable disk 2511 and are distributed. Thecomputer-readable removable disk 2511 includes a flexible disk, acompact disk read only memory (CD-ROM), and a magneto-optical disk. Asemiconductor memory or a hard disk may also be employed. Thus, theapplication programs are installed in the HDD 2505 via the drive unit2513. However, the application programs may be installed in the HDD 2505through a network, such as the Internet, via the communicationcontroller 2517. In the computer, the above-discussed hardware (e.g.,the CPU 2503 and the memory 2501), the OS, and the application programsclosely cooperate so that the above-discussed various functions arerealized.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinvention have been described, in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A method executed by a packet analysis apparatusfor analyzing packets including voice packets and non-voice packets, themethod comprising: capturing packets in a specific session; storing thecaptured packets in a storage; screening the stored packets to count upa receipt count of voice packets in accordance with predefinedcharacteristics of non-voice packets, wherein the non-voice packets aredual tone multiple frequency (DTMF) packets of a DTMF event, and thepredefined characteristics of non-voice packets include at least one ofa retransmission count of the DTMF event, a duration of each DTMFpacket, and a transmission interval of the DTMF packets, theretransmission count representing how many times a terminal packet hasbeen retransmitted, the terminal packet being a DTMF packet transmittedas a last packet of the DTMF event, the duration being represented by atime stamp since a start time of the DTMF event, the transmissioninterval being an interval of transmissions of packets; determiningwhether packet loss has occurred in the specific session; determining,by the packet analysis apparatus, by substantially eliminating aninfluence of the non-voice packets, whether loss packets are voicepackets in accordance with received packets adjacent to the loss packetsto count up a loss count of voice packets when the packet loss hasoccurred, determining whether the loss packets are succeeded by aretransmitted packet of the terminal packet or by DTMF packets includingthe retransmitted packet of the terminal packet; calculating a totalcount of packets from a lead packet to the terminal packet of the DTMFevent including the retransmitted packet by dividing a duration includedin the retransmitted packet by a transmission interval of the DTMFpackets when the loss packets are succeeded by the retransmitted packetof the terminal packet or by DTMF packets including the retransmittedpacket of the terminal packet; and determining whether the loss packetsare voice packets or DTMF packets in accordance with an amount of DTMFpackets succeeding the loss packets, the retransmission count of theterminal packet, and the total count of packets from the lead packet tothe terminal packet of the DTMF event.
 2. A method executed by a packetanalysis apparatus for analyzing packets including voice packets andnon-voice packets, the method comprising: capturing packets in aspecific session; storing the captured packets in a storage; screeningthe stored packets to count up a receipt count of voice packets inaccordance with predefined characteristics of non-voice packets, whereinthe non-voice packets are dual tone multiple frequency (DTMF) packets ofa DTMF event, and the predefined characteristics of non-voice packetsinclude at least one of a retransmission count of the DTMF event, aduration of each DTMF packet, and a transmission interval of the DTMFpackets, the retransmission count representing how many times a terminalpacket has been retransmitted, the terminal packet being a DTMF packettransmitted as a last packet of the DTMF event, the duration beingrepresented by a time stamp since a start time of the DTMF event, thetransmission interval being an interval of transmissions of packets;determining whether packet loss has occurred in the specific session;determining, by the packet analysis apparatus, by substantiallyeliminating an influence of the non-voice packets, whether loss packetsare voice packets in accordance with received packets adjacent to theloss packets to count up a loss count of voice packets when the packetloss has occurred, determining whether the loss packets are preceded bya retransmitted packet of the terminal packet; and determining whetherthe loss packets are voice packets or DTMF packets in accordance with alocation of the terminal packet and the retransmission count of theterminal packet when the loss packets are preceded by a retransmittedpacket of the terminal packet, the location of the terminal packet beingdetermined in accordance with a duration included in the retransmittedpacket.
 3. A method executed by a packet analysis apparatus foranalyzing packets including voice packets and non-voice packets, themethod comprising: capturing packets in a specific session; storing thecaptured packets in a storage; screening the stored packets to count upa receipt count of voice packets in accordance with predefinedcharacteristics of non-voice packets, wherein the non-voice packets aredual tone multiple frequency (DTMF) packets of a DTMF event, and thepredefined characteristics of non-voice packets include at least one ofa retransmission count of the DTMF event, a duration of each DTMFpacket, and a transmission interval of the DTMF packets, theretransmission count representing how many times a terminal packet hasbeen retransmitted, the terminal packet being a DTMF packet transmittedas a last packet of the DTMF event, the duration being represented by atime stamp since a start time of the DTMF event, the transmissioninterval being an interval of transmissions of packets, determiningwhether packet loss has occurred in the specific session; determining,by the packet analysis apparatus, by substantially eliminating aninfluence of the non-voice packets, whether loss packets are voicepackets in accordance with received packets adjacent to the loss packetsto count up a loss count of voice packets when the packet loss hasoccurred, determining whether the loss packets are preceded by a DTMFpacket other than a retransmitted packet of the terminal packet andsucceeded by a voice packet; and determining, when the loss packets arepreceded by a DTMF packet other than the retransmitted packet of theterminal packet and succeeded by a voice packet, that a loss count ofDTMF packets is more than or equals to the retransmission count.
 4. Amethod executed by a packet analysis apparatus for analyzing packetsincluding voice packets and non-voice packets, the method comprising:capturing packets in a specific session; storing the captured packets ina storage; screening the stored packets to count up a receipt count ofvoice packets in accordance with predefined characteristics of non-voicepackets, wherein the non-voice packets are dual tone multiple frequency(DTMF) packets of a DTMF event, and the predefined characteristics ofnon-voice packets include at least one of a retransmission count of theDTMF event, a duration of each DTMF packet, and a transmission intervalof the DTMF packets, the retransmission count representing how manytimes a terminal packet has been retransmitted, the terminal packetbeing a DTMF packet transmitted as a last packet of the DTMF event, theduration being represented by a time stamp since a start time of theDTMF event, the transmission interval being an interval of transmissionsof packets; determining whether packet loss has occurred in the specificsession; determining, by the packet analysis apparatus, by substantiallyeliminating an influence of the non-voice packets, whether loss packetsare voice packets in accordance with received packets adjacent to theloss packets to count up a loss count of voice packets when the packetloss has occurred, calculating a transmission interval of loss packetsin accordance with a difference in time and a sequence number betweenprevious and next packets to the loss packets; determining whether afirst condition has been satisfied, the first condition being that thetransmission interval of loss packets is identical with a transmissioninterval of voice packets and is not identical with a transmissioninterval of DTMF packets; determining that the loss packets are voicepackets when the first condition has been satisfied; determining whethera second condition has been satisfied, the second condition being thatthe transmission interval of loss packets is not identical with thetransmission interval of voice packets and is identical with thetransmission interval of DTMF packets; and determining that the losspackets are DTMF packets when the second condition has been satisfied.5. A method executed by a packet analysis apparatus for analyzingpackets including voice packets and non-voice packets, the methodcomprising: capturing packets in a specific session; storing thecaptured packets in a storage; screening the stored packets to count upa receipt count of voice packets in accordance with predefinedcharacteristics of non-voice packets, wherein the non-voice packets aredual tone multiple frequency (DTMF) packets of a DTMF event, and thepredefined characteristics of non-voice packets include at least one ofa retransmission count of the DTMF event, a duration of each DTMFpacket, and a transmission interval of the DTMF packets, theretransmission count representing how many times a terminal packet hasbeen retransmitted, the terminal packet being a DTMF packet transmittedas a last packet of the DTMF event, the duration being represented by atime stamp since a start time of the DTMF event, the transmissioninterval being an interval of transmissions of packets; determiningwhether packet loss has occurred in the specific session; determining,by the packet analysis apparatus, by substantially eliminating aninfluence of the non-voice packets, whether loss packets are voicepackets in accordance with received packets adjacent to the loss packetsto count up a loss count of voice packets when the packet loss hasoccurred, obtaining a solution of a set of simultaneous equations when atransmission interval of voice packets differs from a transmissioninterval of DTMF packets, the set of simultaneous equations having asvariables an amount of voice packets and an amount of non-voice packetsout of packets to be calculated, the packets to be calculated includingthe loss packets and a packet that succeeds the loss packets; andcalculating the loss count of voice packets and a loss count of DTMFpackets in accordance with the solution of the set of simultaneousequations.